Short Shaft Fan Clutch

i measured my shroud yesterday and could maybe fir an 18" fam but its close. think i'm better off with a 17"

this note is under the Hayden 3618 specs..
"Notes:For use with standard duty fan clutches only. Not for use on engines over 250 cubic inch."

not sure what thats all about..


the Derale 17117 doesn't list any limitations. we shouldn't be turning th emotor so high. probably go with that one then.